Rodentia. MAMMALIA. Rodentia. 
tribal Jistinctions from Mas especially require to be 
signalized, would result iu an evil of far more conse- 
quence than the breach of a rule of nomenclature.” 
The sub-genus Vesperimus — the composition of the 
name ])robably referring to the crepuscular habits of 
the animal — is characterized by a size of body 
medium or small, and by its lithe form and quick 
movements. The eyes are large and prominent; the 
snout pointed. The ears are large, rounded, thin 
and sparsely set with hairs. The tail is terete, slen- 
der, closely hairy, '['he pelage is soft, close and 
glossy, with a few long bristly hairs. The skull is 
thin and papery, contrasting strongly with the 
Arvicolirim in this respect. 'I'he dental structure is 
equally weak, and the habits of the creatures fully 
correspond, the diet being of softer substances. 
WHITE-FOOTED OR DEER MORSE {Hesperomys 
( Vesperimus) leueopus). — 'i'his little animal is called by 
Pennant, A.mkrican Field Mouse; by Godman, Mus 
agrarius ; by Baird, H. myoides and H. gambeli ; by 
the latter, also, H. boylii, in Proc. Acad. N. S., 
Phila., 18.55 ; and by DeKay as Arvicola emmonsii. 
Numerous other synonyms are recorded; this is ac- 
counted for by the fact that a great variety is found 
throughout the extensive range of the species. Dr. 
Coues says : “ It is curious to observe that almost 
every considerable geographical area within the 
limits” of its habitat, “produces a slight strain or 
breed of its White-footed IMice.” * * * “ IVe 
venture to assert that we can distinguish in North 
America about twenty kinds of Hesperomys leueopus, 
upon characters at least as constant, reliable and 
tangible, as those hitherto held to define the greater 
part of the ‘species’ that have been in vogue of late 
years.” The habitat of this animal is throughout 
the northern portion of North America, as far as 
Puget’s Sound, to California on the west, and Massa- 
chusetts on the east. 
A species, or sub-species, called H. leueopus gossi- 
pinus, Leconte, inhabits the South Atlantic States. 
It is larger than the preceding, being about four 
inches in length, with a shorter tail. Another is 
called 11. leueopus sonoriensis, Leconte. It is the 
]\lus leueopus of Richardson, and H. nebrascensis of 
Baird. 'I'he tail is shorter than in the first-named, 
it inhabits the interior of North America, west of 
the Mississippi, and from the Arctic regions to 
Mexico. Another form is the LL. leueopus eremicus, 
Baird — 'I'he Desert-Mouse, from the Valley of the 
Gila, and Colorado. It is about as large as the first- 
named. 
RED MORSE ; GOLDEN MORSE {H. ( Vesp.) aureolus, 
[Aud. and Bach.) Wag.) — 'J’his is like the preceding- 
in size and shape, but different in color, “ being a 
golden-cinnamon above, and yellowish-white or pale 
buff below.” Found in the Central and Southern 
States. Baird records this as M. nuttalli. 
THE MICHIGAN MORSE (^LI. ( Vesp.) michiganensis, 
{Aud. and Bach.) Wag.) — A very small species, rarely 
three inches in length ; yellowish-brown above, with 
a broad dorsal stripe of sooty-brown ; below, pure 
white. 'I'he feet are not entirely white. Habitat, 
Upper Jlississippi A^alley. 
xcv 
PARASITIC MORSE {11. calif ornicus, {Gamhel) 
Baird ). — 'J'his is about the size of a “half-grown 
House-rat, with extremely long ears and tail.” Hab- 
itat, Southern and Lower California. 
THE AZTEC MORSE {11. {Vesp.) aztecus, DeSaus- 
sure). — A Mexican species, about three and three- 
quarter inches in length, the tail averaging over four 
inches. 
BLACK-EYED MORSE {H. {Vesp.) melanophyrs, 
Coues ). — Has the “general aspect of a large species 
of the Hesperomys leueopus group.” The ears are 
large and leafy ; whiskers very long and conspicuous ; 
length four inches ; tail four and a half to five inches. 
Habitat, Southern iMexico. 
Sub-Genus — Onychojiys. — Baird. 
'I'he skull in this genus is strictly as in the preced- 
ing, but with larger molai'S. 
MISSORRI MOLE MORSE {Hesperomys {Onycliomys) 
leucogaster, Max .) — Maximilian procured this during 
his journey in North America, and the type is now 
owned by the American IMuseum, Central Park, 
N. Y. It is found in the Upper Missouri region. 
ARIZONA MOLE MORSE {H. {Ony.) torridus, 
Coues). — 'I'liis form is from Arizona. It was described 
by Dr. Coues, in 1874, in Proc. Acad. Nat. ScL, Phil. 
It resembles the latter, with rather larger limbs. 
Sub-Genus — Oryzomys. — Baird. 
'I'his is characterized by having the superior mar- 
gin of the orbit with a prominent sharp edge or 
bead. 'I'he anteorbital foramen is nearly circular 
above (resembling that in Zapodidee), continued be- 
low as a slit much narrower than iii Hesperomys 
proper, '['he hind-legs are short, but the feet are 
very long and large, as in Fiber. It exceeds in size 
any other known species of Hesperomys, and has the 
general appearance of Sigmodon or j\Ius. The 
species approach the true Mus of the Old World 
more closely than any other of our Rodents. 
RICE-FIELD MORSE {Hesperomys { Oryzomys) pal- 
ustris, {Harl.) Wagner). — 'i'his is the Arvicola orizi- 
vorM of Aud. and Bach., the specific term referring to 
its rice-eating propensities, 'i'he sub-genus is named 
from oryza, the Greek for Rice, mys being from the 
Latin mus, a Mouse. 'This species is especially well 
known in the Southern rice-fields, extending to the 
Gulf States. 
Reithrodon. — Waterhouse. 
Several species were included in this genus by Prof. 
Baird {Mam. N. A.), but, as now restricted, “the 
genus,” says Dr. Coues, “appears to be confined to 
the southern part of South America, from which 
three species have been described. It may be recog- 
nized at once by the longitudinal grooving of the 
upper incisors, a feature not shared by any other 
South American Mice, as far as is known, and only 
again met with among American Muridee, in the 
North American genus Ochetodon.” 'I’he latter is 
in other respects, very unlike Reithrodon, which has 
a stout leporine form, of large size, and tail half as 
long as the trunk. 
